Preliminary procedure for conditioning wells



atented Aug. 11, 1936 ml'rlaio STATES PRELIMINARY PROCEDURE FOR CONDITIONING WELLS Melvin De Groote, St. Louis, Mo., assignor to Tretolite Company, Webster Groves, 'Mo., a

corporation of Missouri N Drawing.

8Clalms.

This invention'relates to processes of the kind that are used for increasing the productivity of deep wells, such as oil wells, gas wells, water wells and brine wells.

When an oil well is drilled into an oil-bearing stratum, the release of pressure upon the oil deposit may cause the oil to flow naturally for a certain period of time, after which the volume of flow will, in most instances, gradually decrease o to a point or degree where some procedure, such as pumping, must be employed, so as to insure the production of a profitable amount of oil. Thereafter, production may continue to decline until the quantity of oil obtained from the well is so small that it is not commercially practicable to continue thewell in operation- In some instances the stoppage of oil output or decline in production, above referred to, is not caused by exhaustion of the oil supply, but, on the contrary, is caused by building up of soliddeposits of wax, or of inorganic salts, in the channels or pores of the oil-bearing rock. The productivity of wells of the kind above mentioned may, in some instances, be wholly, or at 5 least partially, regenerated by mechanical means, such as the use of an explosive, but there are various objections to such mechanical treat- *mentysuch as the high cost and danger of iniuring the internal well structure itself. a In such instances where the hydrocarbon gases, escaping from a well, lower the solubility of wax or paraflln bodies in the oil, with the result that wax or paraffin-like bodies are deposited in the oil-bearing stratum, one is confronted with considerable difliculty in attempting to remove such wax or paraflin-like bodies,

due to their chemical inactivity. Asphaltic ma-;

terials may act the same as wax. Indeed, it is not necessary for the oil-bearing strata to be 40 clogged entirely with wax or paraflln-like bodies, but, on the contrary, a mere coating or fllm of wax or paraifin on calcareous matter sometimes prevents ordinarily effective acid-treating agents, such as hydrochloric acid, from combining with 55 or removing the calcareous deposit, and thus presents the same sort of difliculty. The present invention consists of a preliminary procedure for conditioning-wells, and-involves the removal of such films of wax, paraiiflnlike-bodies, or simm ilar matter, from calcareous deposits, or siliceous structures, so as to render said deposits or structures susceptible totreatment with hydrochloric acid ydrofluoric acid, generated in situ, or such other acid treating agents as may as be employed. Before describing the process in carbonate.

Application February 1' 1936, Serial No. 64,346

detail, it may be well to point out the general features involved in hydrofluoric acid treatment, as well as the treatment involving the generation or hydrofluoric acid in situ.

"or a formation related to calcareous or magnesian formation, provided the clogging is due eso sentially to uncoated calcium carbonate or magnesium carbonate or the like. This is also true in such siliceous or similar strata, from which petroleum oil is derived, where there is a clogging of the oil sands, due to the presence of alkaline earth carbonates, and primarily calcium It is believed that the subterranean water becomes saturated with calcium blcarbonate under pressure, and that when the well is drilled and pressure released, some of the subterranean water escapes with the oil, with the result that the solubility of the calcium carbostratum. So far as the usual hydrochloric acid treatment is concerned, it is immaterial whether the formation itself is truly calcareous or arglllaceous, or is a siliceous formation with a calcareous deposit.- Naturally, magnesium carbonate deposits are susceptible to treatment as calcium carbonate deposits.

Obviously, if hydrochloric acid treatment is applied to an oil-bearing limestone formation, it may not only remove any deposited calcium carbonate or the like, but .it may increase the porosity of the limestone structure itself. Therefore, in actual use, the increased productivity is not limited to the removal of the relatively recent calcium deposit, but it may also be concerned with the increased natural porosity of the aged oil-bearing stratum itself. some oilbearing strata are not essentialLv calcareous in character, but may essentially be siliceous in character, or else, may represent limestone so high in siliceous content that there is limited or no chemical reactivity towards hydrochloric acid.

It is well known, of course, that hydrofluoric 5o acid attacks silica, with the resultant production of water and silicon tetra-fluoride, the latter being a "gas. Commercial efforts have been made to use hydroflucric acid to increase .the production of oil wells. Hydroflucric acid, of course, as

.could be emulsifled so as to produce a hydrofluoric acid in oil emulsion in the manner described in U. S. Patent No. 1,922,154, dated April 15, 1933, to Melvin De Gmote. Another method is to employ a salt of hydrofluoric acid, such as sodium fluoride. which is non-corrosive,-

and' permits reactions totake place with a suitable acid, such as hydrochloric acid or nitric acid insitu. Such a process. is described in .U. S. Patent No. 1,990,969, dated February 12,

1935, to Wilson.. Another method, described in my pending application for patent Serial No.

55,614 flied December ,21, 1935, employs a solution of sodium fluoride or suspension of sodium fluoride, or any other suitable fluoride, such as calcium fluoride, in the'form of an emulsion, so

as to produce a water-in-oil emulsion admixed with another emulsion of hydrochloric acid in oil. .Such an emulsion contains two different internal phases, one an aqueous sol or suspension of sodium fluoride, and the other being aqueous hydrochloric acid, which do not re-act until the emulsion is injected into the stratum .and breaks, due to the capillarity of the structure.

' In view of what has been said previously, it

treatment becomes questionable.

process consists oi an improvement on older is obvious that the success of an acid treating process depends upon the ability of the acid to contact the material to be removed, i. e., the

deposits of calcium carbonate, magnesium carbonate, or silica. If the calcium carbonate, magnesium carbonate, or siliceous structure is covcred-with an oily or wax-like body, successful The present processes, and is intended primarily for use in conjunction with strata which appears to be coated with a fllm of waxy, asphaltic, or paraffln-like bodies. .Briefly described, the present process consists in dissolving an oil and watersoluble wetting agent, which is preferentially water-soluble, such as a petroleum sulfonate, in

an oily liquid, such as crude oil, gasoline or. some other suitable solvent, and then forcing the said solution through the area or structure to be suuently treated with acid. After this flrststage of treatment, water, or water with a dissolved water-soluble wetting agent (which may not have any oil solubility whatsoever), is forced through the area being treated. This second stage is then followed by a conventional acid treatment employing hydrochloric acid, 'hyabsence of the other kind of a solvent, 1. e., they will dissolve in oil in the absence of water, and will dissolve in water in the absence of oil, but if at freedom to do so, they will pass from oil into water, but not from water into oil.

In the mt, efiorts to remove the waxy film or asphaltic fllm from the surface to be treated, .genera depended uponeither one of two procedures, one of, which procedures involved passing a solvent suchas kerosene, crude oil and gasoline through the area to be subsequently treated, and the other procedure involved flushing said area with an aqueous solution containsolution or as an aquesol for conventional flood- -lene, sulfonic acid, ammonium salt.

ing a wetting agent of the type which has been employed in recovering oil from depleted oil sands. Reagents of the type lastreferred to are disclosed'in U. S. Patent No. 1,823,439, dated September 15,1931, to Melvin'pe Groote; U. S. 1 Patent No. 1,823,440, dated September 15, 1931, to Melvin De Grooteand Louis ,T; Manson; and U. S. Patent No. 1,894,759, dated- January 1'1,

'1933, to Melvin De Groote and Arthur F. Wirtel.

The relative ineffectiveness of a solvent is It explainable perhaps by an analogy to an adsorbed material on charcoal, and also due to the fact that the surface remains coated with an oily body. If an aqueous solution is clarified by means of charcoal, the material removed from it the solution is adsorbed on the charcoal in the same manner that-waxy material may be adsorbed from a hydrophobe sol, that is. from the crude petroleum, onto the deposits to be acid treated. If the charcoal with its-adsorbed fllm 2(1 is washed with water, it will be found that usually the washing process does not remove the adsorbed fllm, i. e., the previous water-soluble or water-dispersible material does not re-dissolve or re-disperse in water by mere contact 25 with water. Similarly, by analogy, the mere passing of crude oil or kerosene, or some other solvent, through or over the surface to be acid treated, may no longer remove the adsorbed wax or hydrophobe material which may have 30 been at one time rather oil-soluble, or at least, oil-dispersible.

The ineffectiveness of materials, for instance, wetting agents of the kind employed in aqueous 35 ing oil sands, is probably explained by the fact that the solution, although having apparently a preferential wetting property, still does not dislodge the adsorbed fllm, principally because the material employed as a wetting agent is only 4 water-soluble, or, if it is both oil and watersoluble, it will not leave the aqueous solution, or will not pass from the hydrated state into the oily, or perhaps wax-like, fllm on the adsorbed structure. a However, when a subterraneanstructure with its adsorbed fllm of wax or similar material is contacted with an oil and water-soluble wetting agent dissolved in oil, for instance, a petroleum sulfonate derived from a mahogany acid or M acids and in the form of a sodium salt, then the oil and water-soluble dispersing agent appears to adsorb from the oily vehicle onto the waxlike material and become a part thereof of the adsorbed layer. Subsequently, when water is 5: forced through the structure, the previously adsorbed wetting agent, although oil-soluble in absence of water, becomes water-soluble, because, as previously stated, it must be of the kind which is preferentially water-soluble. Thus, the ad e41 sorbed waxy film or the like is removed, disrupted or dislodged.

The water, which is passed through the structure to wash of! or remove the asphaltic fllm, may contain, if desired, a suitable water-soluble 65 reagent, such as mono-butylated, beta naphtha- I have found that such treatment as herein described will often cleanse the surface of the structure, so that subsequent treatment with a suitable acid of the kind ordinarily employed in acid treatment, will be readily effective. The reagent, which I prefer to employ in the hydrophobe solution, is a petroleum sulfonate inthe form of a sodium salt derived from mahogany acids, is

because such material is'relatively cheap and exhibits an excellent solubility, both in oil and water. Other similar materials may be employed, such as the material obtained by neutralizing the sulfoacid hydrogen of sulfo oleic acid with ammonium hydroxide and esterifying the carboxylic acid hydrogen with a suitable alcohol, such as methyl, ethyl, propyl, or butyl alcohol. Other suitable oil and water-soluble wetting reagents include the amylamine or butylamine salt of propylated or butylated naphthalene sulfonic acids, etc. 'Other amine salts, such as benzylamine salts, toluidine salts, etc., of various alkylated naphthalene suli'onic acids may be employed.

The percentage of oil and water-soluble wetting agent dissolved in the oil used in the first flushing step, may *vary' from to 5%, depending upon the reagent employed. I prefer to use crude petroleum oil as the oily vehicle, but kerosene, gasoline, sulfur dioxide extract of the kind obtained in the petroleum refining, solvent naphtha, benzol, tar acid 011, etc., could be used. Similarly, if a water-soluble wetting agent is added to the water used in the second flushing step, the amount may vary similarly, depending upon the kind of the wetting agent employed, but

/2% to 5% usually is'a reasonable range. In some instances, the productivity of a well may be increased by the flushing procedure or treatment herein described, without subsequent acid treatment, although as a rule, it is more desirable to employ the said treatment immediately after the flushing procedure, so that the surfaces to be attacked by the acid are in clean condition, susceptible to reaction.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A preliminary procedure for conditioning a well. characterized by introducing into the producing stratum a hydrophobe solution of a water and oil-soluble wetting agent which is preferentially water- -soluble to the extent that it will not pass from an aqueous phase into an oil phase and is oil soluble only in the substan- 2. A preliminary procedure for conditioning,

a well, characterized by introducing into the producing stratum a hydrophobe solution of a Patent No 2,050,931.

water and oil-soluble wetting agent derived from a. mahogany petroleum sulfonic acid and being preferentially water-soluble to the extent that it will not pass from an aqueous phase into an oil phase and is oil soluble only in the substantial absence of water, and thereafter flushing the producing stratum with a suitable aqueous medium.

3. A preliminary procedure for conditioning a well, characterized by introducing into the producing stratum a hydrophobe solution of a water and oil-soluble wetting agent derived from an esterified sulfo-oleate and being preferentially water-soluble to the extent that it will not pass from an aqueous phase into an oil phase, and is oil soluble only in the substantial absence of water, and thereafter flushing the producing stratum with asuitable aqueous medium."

4. A preliminary procedure for conditioning a well, characterized by introducing into the producing stratum a hydrophobe solution of a water and oil-soluble wetting agent water-soluble and derived from a higher amine salt of alkylated naphthalene sulfonic acid and being preferentially water-soluble to the extent that it will not 5. A preliminary procedure for conditioning a well, characterized by introducing into the producing stratum a hydrophobe solution of a water and oil-soluble wetting agent which is preferentially water-soluble to the extent that it will not pass from an aqueous phase into an oil phase and is oil soluble only in the substantial absence of water, and thereafter flushing the producing stratum with an aqueous solution of a wetting agent.

6. A preliminary procedure for conditioning a well, characterized by introducing into the producing stratum a hydrophobe solution of a water and oil-soluble wetting agent which is preferentially water-soluble'to the extent that it will not pass from an aqueous phase into an oil phase and is oil soluble only in the substantial absence of water, and subsequently flushing the producing stratum with a suitable aqueous medium comprising an aqueous solution of monobutylated, beta naphthalene, sulfonic acid ammonium salt.

MELVIN DE GROOTE.

CERTIFICATE OF CORREGTION It ishereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: 0 line 22, claim 4, strike out the words Water-soluble and"; and that the said Letters Patent should. be read with this correction therein that the August 11, 1936.

MELVIN DE GROOTE same may conform to the record of the case in the Patent Office.

Signed and sealed this 6th day of October, A. D. 1956.

(Seal) Henry Van Arsdale "Acting commissioner of Patents.

Page 3, second CERTIFICATE or CORRECTION.

Patent No. 2,050,931.

MELVIN DE GROOTE.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, second column, line 22, claim 4, strike out the words 'water-rsoluble and"; end that the said- Letters Patent should. be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 6th day of October, A. D. 1936.

v Henry Van Arsdalb (Seal) lming Commissionerof Patents.

August 11, 1936. 

